The power of observation to improve the quality of teaching can be greatly increased through the use of video. The disadvantages of intrusiveness, anxiety and selectivity are usually outweighed by its advantages:
Video enables the teacher to study and to some extent objectify his/her practice in a way which even the most sympathetic and insightful of observers cannot.
Video facilitates precision in post-observation analysis, because both teacher and observer can select particular episodes - problematic or otherwise - for detailed scrutiny and discussion.
Video allows the teacher to re-visit his/her teaching not just once (via the post-observation discussion) but over and over again. Users of video testify to the way each viewing produces new insight and understanding, and sharpens the teacher's awareness of the strengths, weaknesses and development points in his/her practice.
If those who have been videoed agree to release their tapes for this purpose, a department can build up a stock of such material for study by probationers and others who wish to reflect on and/or improve their teaching.
In fact, the problems of intrusiveness and anxiety are more apparent than real: most users of video in teaching acclimatise to it much more quickly than they expect. As for the selectivity of video, in this context it is as much an advantage as a problem.
Video is not as widely used in staff development as it deserves to be. As well as commending it as an extremely valuable tool for improving teaching, the Staff Development Office would be interested to hear from those who have used and benefited from it.